十论现代表面工程

表面加工技术可以追溯到古代,后来形成油漆、电镀、热喷涂三个行业.20世纪60年代,电子束、离子束和激光束进入表面加工技术领域,引发了表面技术翻天覆地的变化与进步,逐步形成现代表面工程学.以最简要的方式论述了现代表面工程的确切定义、两大使用原则、三大技术、四大功能、表面工程学的形成.现代表面工程的确切定义为:物体表面施加保护层的理论、技术、材料、工艺和标准称为表面工程.两大使用原则为表面与整体同时进行设计制造的原则、建立和维持表面保护层完整性原则.三大技术包括表面改性转化技术、薄膜技术和涂镀层技术.四大功能包括控制腐蚀、摩擦润滑匹配、表面功能转化和表面装饰.表面工程学包括坚实的理论基础、雄厚的技术内涵、表面保护层的设计、实施工程车间的设计与检测和不同领域广泛的应用研究.     

水淘洗法分离镍基高温合金粉末中陶瓷类夹杂物

详细介绍了水淘洗方法分离固体颗粒的原理,从实践上建立了镍基高温合金粉末陶瓷类夹杂物的分级分离法,进行实验验证,并分析了水淘洗方法的可靠性。     

梦·热处理

评述了钢中马氏体相变、铝合金中时效析出相变、高温合金表层组织再造改性微观机理研究进展,及其对先进热处理发展的推动作用。认为先进热处理赋予材料极限性能和构件极限服役行为,是先进材料和高端机械制造的核心技术。转变观念,快速、高效发展先进热处理,是发展先进材料和高端制造、建设材料和机械制造强国的必由之路。提出了中国热处理技术发展路线图架构设想。     

Effects of crystallographic orientations and dwell types on low cycle fatigue and life modeling of a SC superalloy

Effects of temperature (760 °C and 980 °C), crystallographic orientation ([0 0 1], [0 1 1] and [1 1 1]) and dwell types (tensile, compressive and balanced dwell type) on low cycle fatigue (LCF) of a Ni-based single crystal (SC) superalloy are experimentally investigated and modeled. Since the LCF behavior shows strong crystallographic orientation and dwell type dependences, corresponding accurate life models are needed for safe application in gas turbine components. The feasibility of stress-based, strain-based and energy based models on anisotropic fatigue behavior was evaluated. A modified Cyclic damage accumulation (CDA) method combined with critical slip plane concept is developed to correlate the influence of orientation and dwell type on LCF data.     

Mechanical characterization of open cell aluminium foams reinforced by nickel electro-deposition

The present study focused on the improvement of mechanical properties of open cell aluminium foams thanks to electro-deposition of nickel. In the first phase of the work, the parameters for the electro-deposition of nickel were optimized in order to increase the mechanical properties of these cellular materials. Different values of deposition currents and times were considered to vary the amount of nickel deposited. The performance improvement was evaluated by means of stress–strain curves. Strains were measured using a specifically developed optical extensometer with a resolution in strain of 14.1 micro-strains. A very low compression speed was set to provide a good temporal resolution given the type of camera used. Mechanical properties of aluminium foams coated by nickel or copper were compared according to the defined procedure to identify the effect of material and thickness of the coating. Stiffness was found not to be significantly affected by the electro-deposition of copper or nickel. On the contrary the maximum specific stress has been dramatically improved by the nickel coating.     

The role of oxidation damage in fatigue crack initiation of an advanced Ni-based superalloy

The effects of prior oxidation on the room temperature fatigue life of coarse-grained Ni-based superalloy, RR1000, have been investigated. High cycle fatigue tests were conducted, on both machined and pre-oxidised testpieces, at room temperature at an R ratio of 0.1. The oxidation damage was produced by pre-exposures at 700 °C for either 100 or 2000 h. Pre-oxidised testpieces tended to fail with shorter fatigue lives than those obtained from the as-machined testpieces although they were also observed to outperform the as-machined test pieces at peak stress levels around 900 MPa. The chromia scale and intergranular alumina intrusions formed during pre-oxidation are prone to crack under fatigue loading leading to early crack nucleation and an associated reduction in fatigue life. This has been confirmed to be the case both below and above a peak stress level of ∼900 MPa. The better fatigue performance of the pre-oxidised specimens around this stress level is attributed to plastic yielding of the weaker γ′ denuded zone, which effectively eases the stress concentration introduced by the cracking of the chromia scale and intergranular internal oxides. This γ′ denuded zone is also a product of pre-oxidation and develops as a result of the selective oxidation of Al and Ti. Over a limited stress range, its presence confers a beneficial effect of oxidation on fatigue life.     

新型水基薄膜润滑剂在高强度螺栓连接副上的应用研究

介绍一种新型水基薄膜润滑剂。仅利用该润滑剂对高强度螺栓连接副中的螺母表面进行润滑处理,即能够达到以下目的:处理后的磷化大六角头螺栓连接副,在0～60℃时,其扭矩系数及标准偏差均满足GB/T1231—2006《钢结构用高强度大六角头螺栓、大六角螺母、垫圈技术条件》的要求,且温度每变化10℃,扭矩系数的变化率仅为2.7%;处理后的磷化扭剪型螺栓连接副,在0～60℃时,其紧固轴力均满足相关标准要求,且其标准偏差远低于标准允许范围;处理后的达克罗大六角头螺栓连接副,其扭矩系数及标准偏差亦能够满足相关标准要求。     

Localized dissolution initiated at single and clustered intermetallic particles during immersion of Al–Cu–Mg alloy in sodium chloride solution

Aiming at understanding how intermetallic phases response when AA2024-T3 aluminium alloy is exposed to chloride-containing aqueous medium, scanning electron microscopy was employed to provide morphological information on alloy surface before and after corrosion testing. Energy dispersive X-ray spectroscopy was carried out to determine compositional change in intermetallic particles. Atomic force microscopy was used to examine topographical variation introduced by the reactions of intermetallic phases. Transmission electron microscopy combined with ultramicrotomy was carried out on dealloyed Al₂CuMg particles and their periphery region. It is found that dealloyed Al₂CuMg particles exhibited porous, polycrystalline structure comprised of body-centred cubic copper particles with sizes of 5 to 20 nm. Aluminium matrix started to trench in the periphery of Al₂CuMg particles at the early stage of dealloying. Development of trenching in Al–Cu–Fe–Mn–(Si) particle's periphery was not uniform and took longer time to initiate than Al₂CuMg dealloying. Localized corrosion at a cluster of Al₂CuMg and Al₂Cu particles was mainly associated with Al₂CuMg particles.     

Joining of Si3N4 to Si3N4 using a AuPd(Co,Ni)–V filler alloy and the interfacial reactions

Au38.0–Pd28.0–Co18.0–Ni7.0–V9.0 (in wt%) alloy was designed as a filler for joining Si₃N₄. The filler alloy showed a contact angle of 77.2° on Si₃N₄ ceramic at 1473 K. The Si₃N₄/Si₃N₄ joint brazed with the rapidly-solidified filler foils at 1443 K for 10 min exhibits an average three-point bend strength of 320.7 MPa at room temperature and the strength values are 217.9 MPa and 102.9 MPa at 1073 K and 1173 K respectively. The interfacial reaction products were composed of V₂N and Pd₂Si, and the elements Co and Ni in the brazing alloy did not participate in the interfacial reactions. The coarse-network-like distribution of refractory Pd₂Si compound within the Au–Pd–Co–Ni alloy matrix throughout the joint contributes to the stable high-temperature joint strengths.     

制取铸造Al-Si合金EBSD样品的方法

铸造Al-Si合金的组织特殊,制取EBSD样品时难度较大.本文综述了目前常用的制取铸造Al-Si合金EBSD样品的方法,包括电解抛光、离子铣削和震动抛光,对不同方法在实验周期、可操作性、成本及样品表面质量等几方面的表现进行了对比分析.并以ZL114A合金作为实际操作合金,利用上述方法制备样品,进行EBSD分析,实验结果...